Temperature correction devices and techniques are used in a wide variety of environments for commercial and industrial applications. For example, temperature correction devices and techniques may be used for correcting for the temperature of fluids (gas and/or liquid) in pipelines or storage facilities. Many volumetric gas flow meters, for instance, require temperature correction to properly register the amount of gas passing therethrough. Such devices may use mechanical or electrical techniques to perform the temperature correction.
Common temperature correction devices and techniques use resistive thermocouples, resistive temperature devices, gas-filled Bourdon tubes, or bimetal coils to sense temperature. Bimetal coils have found favor because they may be readily manufactured at low cost, have good accuracy, and have long-term stability.
Bimetal coil temperature measurement devices include a bimetal coil that torsionally responds to temperature changes. A shaft is commonly disposed through the center of the coil and coupled to the coil at one end. The shaft is also commonly coupled to an indicator assembly. In operation, when the coil responds to a temperature change, the torsion is relayed to the shaft, causing it to rotate. The rotation of the shaft is then relayed to the indicator assembly, which produces an indication of the temperature sensed by the coil. Thus, a technician may read the temperature at the device.
When calibrating a temperature measurement device that uses a bimetal coil for measurement of natural gas, the device is commonly inserted into a bath at 60° F., which is the standard base temperature for natural gas. If the device does not indicate 60° F., the device is extracted from the bath and either portions of the coil are welded together or portions of the coil are welded to other components of the device. The device is then inserted into the bath again and checked for proper indication. This process of checking for proper indication and welding together of components to compensate for inaccuracy may be continued over several cycles.